This disclosure pertains to a method and apparatus of containing molten aluminum using a barrier layer of a non-wetting material.
Thermal evaporation is a very common method of depositing thin films of aluminum. In this technique, aluminum shot is placed into a crucible that is typically made of graphite, a refractory metal, or an oxide, and heated using either an electron beam or resistive coils. Unfortunately, molten aluminum has a strong propensity to wet most crucible materials and is highly corrosive to refractory metals, such as tungsten and molybdenum. As the molten aluminum creeps during the deposition, it can wet out onto other system elements, solidify on the backside of the crucible and cause thermal shock and cracking, corrode resistive heating elements, and change the thermal conduction properties of the crucible. This problem is typically managed by frequently replacing crucibles, leading to excess cost and material waste.